Tuesday, April 10, 2007

The Great Global Warming Swindle Review: Part I

As noted in a previous post comments, I recently watched "The Great Global Warming Swindle" thanks to a link from Reliapundit. It was a very interesting program, and I'll comment on it at length. I took quite a few notes, including direct quotes from the documentary, but I should warn that they may have slight errors where I missed a word or two.

There are several points and theories advanced in this video, and I intend to address most of them, with the notable exception of any issues related to the Kyoto protocols or the impacts of any such suggested solutions. This will be a topic that will undoubtedly take up several posts over the next few weeks.

In this first one, I will cover some generalized claims from the movie. Many of the specific claims will be dealt with in subsequent posts:

1."The Earth's Climate Is Always Changing"Yes, it's true that the Earth's climate is always changing and has changed in the past many times with no human intervention. There are several things that can cause changes in the climate: changes in the sun's irradiance, changes in the earth's orbital alignment, changes in the level of particulate matter in the atmosphere, changes in the level of greenhouse gases, and, as this show features prominently, changes in the cloud cover of the planet. But, the number of direct climate drivers is actually relatively small, and at this point, pretty well measured and understood. Climate modeling often takes a hit, because it is essentially impossible to predict how these factors will change, and even what feedback effects will result from maintaining the status quo. However, it is very important to understand the difference between climate modeling to predict the future and climate modeling to explain the past, especially the recent past. When modeling past climate, the factors have all already been determined. The researcher has to measure all of the forcings that were applied to the climate and determine how they should be weighted to best explain the data. When climate scientists make predictions about the future, they are relying on modeling. When they make statements like, "the earth has warmed ~.6 degrees C in the past 30 years and anthropogenic greenhouse gas production is responsible for much of that increase," they are relying on measurements more than modeling.

So, the important fact isn't that the earth's climate changes, it's what's causing the change and with what level of certainty we can make that determination. People often die, but we do autopsies to determine what caused their death when we're not sure of the cause. If it was natural causes, then there is usually no need to delve any further. If it was some type of trauma that caused the death, then there is probably a need for investigation. A scientist saying "the earth's climate is always changing" is like a police officer saying "people die all the time" when pointed to a body lying in the street. It's true, but has little meaning when we can investigate and determine the root cause.

2. There is Nothing Unusual About the Current Temperature ChangeThat brings us to point 2. Is there something different about the current warming that separates it from past warming events? The directors of "Swindle" certainly conclude that there is not any difference. If we look at the past 2000 years of temperature reconstructions we can see that the current warming is easily the greatest temperature reached during that time. Although much is made of the Medieval Warm Period in the movie, the global temperatures at that time were only warm compared to the other temperatures before 1975. The global temperatures during the Medieval Warm Period did not approach the current global average. So, we're currently experiencing warming that, to the best of our knowledge, has not happened in the past 2000 years. Is that unusual? Going back farther, the reconstructions get more divergent and the granularity of measurement gets less, but, taking the average of reconstructions, we are currently warmer than we have been for 12,000 years (note: dark black line is the average of the reconstructions). Is there anything else that we are currently experiencing that is a climate driver that hasn't been this high in 12,000 years? As a matter of fact, there is. CO2. Can a similar claim be made for any of the other climate drivers we've identified? We'll see, in upcoming segments...